Calibration cassette pod for robot teaching and method of using

ABSTRACT

A calibration cassette pod for robot teaching and a method of using the calibration cassette pod are described. In the calibration cassette pod, a cassette pod body and a cassette pod door are first provided wherein the cassette pod body is constructed of a top panel, a bottom panel, two side panels and a front panel to enclose a cavity therein. A first plurality of ribs is formed on an inside surface of the cassette pod body, each having a predetermined depth sufficient to support an edge portion of a wafer. An optical detector housing is mounted on an opening in the front panel and is adapted for receiving an optical detector therein. An optical detector that includes a light emission source and a photo diode receiver for determining the position of the edge portion of the wafer is mounted in the optical detector housing.

FIELD OF THE INVENTION

The present invention generally relates to a calibration cassette podfor robot teaching and method of using and more particularly, relates toa cassette pod equipped with an optical detector including a lightemission source and a photo diode receiver for detecting the positioningof a wafer edge and thus, enables the calibration of a robot arm thatdelivers the wafer into the cassette pod and a method of using thecalibration cassette pod.

BACKGROUND OF THE INVENTION

In the manufacturing of a semiconductor device, the device is usuallyprocessed at many work stations or processing machines. The transportingor conveying of partially finished devices, or work-in-process (WIP)parts, is an important aspect in the total manufacturing process. Theconveying of semiconductor wafers is especially important in themanufacturing of integrated circuit chips due to the delicate nature ofthe chips. Furthermore, in fabricating an IC product, a multiplicity offabrication steps, i.e. as many as several hundred, is usually requiredto complete the fabrication process. A semiconductor wafer or IC chipsmust be transported between various process stations in order to performvarious fabrication processes.

For instance, to complete the fabrication of an IC chip, various stepsof deposition, cleaning, ion implantation, etching and passivation stepsmust be carried out before an IC chip is packaged for shipment. Each ofthese fabrication steps must be performed in a different processmachine, i.e. a chemical vapor deposition chamber, an ion implantationchamber, an etcher, etc. A partially processed semiconductor wafer mustbe conveyed between various work stations many times before thefabrication process is completed. The safe conveying and accuratetracking of such semiconductor wafers or work-in-process parts in asemiconductor fabrication facility is therefore an important aspect ofthe total fabrication process.

Conventionally, partially finished semiconductor wafers or WIP parts areconveyed in a fabrication plant by automatically guided vehicles (AGV)or overhead transport (OHT) vehicles that travel on predetermined routesor tracks. For the conveying of semiconductor wafers, the wafers arenormally loaded into cassettes pods, such as SMIF (standard machineinterface) or FOUP (front opening unified pod), and then picked up andplaced in the automatic conveying vehicles. For identifying and locatingthe various semiconductor wafers or WIP parts being transported, thecassettes or pods are normally labeled with a tag positioned on the sideof the cassette or pod. The tags can be read automatically by a tagreader that is mounted on the guard rails of the conveying vehicle.

An OHT system is frequently used to deliver a cassette pod such as aFOUP to a process machine. This is shown in FIG. 1. A cassette pod 10 ofthe FOUP type is positioned on a loadport 12 of a process machine 14.The loadport 12 is frequently equipped with a plurality of locating pins16 for the proper positioning of the cassette pod 10. A detailedperspective view of the FOUP 10 is shown in FIG. 2. The FOUP 10 isconstructed of a body portion 18 and a cover 28. The body portion 18 isprovided with a cavity 46 equipped with a plurality of ribs 48 for thepositioning of 25 wafers of the 300 mm size. The body portion 18 isfurther provided with sloped handles 50 on both sides of the body forease of manual transportation. On top of the body portion 18, isprovided with a plate member 52 for gripping by a transport arm (notshown) of an OHT system (not shown).

When the cassette pod 10 is positioned on the process machine 14, andthe cover 28 is removed to expose an opening to cavity 46, a robot arm(not shown) equipped with a wafer blade (not shown) is used to unloadwafers from the cassette pod 10 and deliver the wafers to the processchamber of the process machine 14. After the wafer has been processed inthe process chamber, it is again transported by the robot arm back intothe cassette pod 10. The operation or the movement of the robot armtherefore must be accurately calibrated for the wafer pick-up anddelivery operations. When a FOUP is used for storing 300 mm wafers, theFOUP is frequently fabricated of a non-transparent plastic material. Itis therefore difficult to visually detect the movement of the robot arm,i.e and thus the wafer blade, through the housing of the FOUP.

When a robot teaching is poor during an insulation process of theprocess machine or after a preventive maintenance procedure has beenconducted, the poor robot teaching can lead to serious processingdifficulties due to the inaccurate position of the robot arm, i.e. andthus the wafer blade. For instance, when a robot arm reaches into thecavity too deeply, an edge of the wafer may rub against the interiorsurface of the front panel of the housing and thus causing seriousparticle issues. On the other hand, if the robot arm does not reach deepenough into the cavity during the placement of a wafer and thus placinga wafer inaccurately in the cavity, the edge of the wafer may collidewith the FOUP door during a door closing operation. The collision of thewafer with the FOUP door may cause serious damage to the wafer, or mayeven cause breakage of the wafer.

As a result, the robot teaching for picking up or delivering the waferfrom or to a cassette pod cavity must be accurately performed.Presently, the robot teaching is conducted by visual examination withhuman eyes which is frequently inaccurate due to human error or thesubjectiveness of the human operator.

It is therefore an object of the present invention to provide anapparatus for robot teaching that does not have the drawbacks or theshortcomings of the conventional apparatus.

It is another object of the present invention to provide a calibrationcassette pod for robot teaching that can eliminate human error and humansubjectiveness.

It is a further object of the present invention to provide a calibrationcassette pod for robot teaching by installing an optical detector insidethe calibration cassette pod.

It is another further object of the present invention to provide acalibration cassette pod for robot teaching wherein a light emissionsource and a photo diode receiver are installed to detect the positionof an edge portion of a wafer.

It is still another object of the present invention to provide acalibration cassette pod for robot teaching that can be used in aportable manner for calibrating a plurality of robot arms.

It is yet another object of the present invention to provide a methodfor calibrating a robot arm by a calibration cassette pod that does nothave the drawbacks or the shortcomings of the conventional method.

It is yet another object of the present invention to provide a methodfor calibrating a robot arm by a calibration cassette pod wherein arobot arm is first manually operated to load a wafer into a cassettecavity correctly to reset a process controller to zero.

SUMMARY OF THE INVENTION In accordance with the present invention, acalibration cassette pod for robot teaching and a method of using thecalibration pod are provided.

In a preferred embodiment, a calibration cassette pod for robot teachingis provided with include a cassette pod body and a cassette pod door,the cassette pod body is constructed of a top panel, a bottom panel, twoside panels and a front panel defining a cavity therein; a firstplurality of ribs formed on an inside surface of the two side panels andthe front panel each has a preset depth sufficient for supporting anedge portion of a wafer; an optical detector housing mounted on anopening in the front panel adapted for receiving an optical detectortherein; and an optical detector that includes a light emission sourceand a photo diode receiver for determining the position of the edgeportion of the wafer.

In the calibration cassette pod for robot teaching, the light emissionsource may include a second plurality of light emission units and asecond plurality of photo diode receivers. The second plurality may beat least three, and preferably at least five. The calibration cassettepod may further include a process controller for receiving signals fromthe optical detector and comparing to a stored datum. The light emissionsource may emit a visible light beam. The calibration cassette pod mayfurther include a robot arm controlled by the process controller. Theoptical detector may be mounted in the optical detector housing with thesecond plurality of light emission units and the second plurality ofphoto diode receivers protruding into the cavity of the cassette podbody. The cassette pod body when installed on a loadport of a processmachine with the cassette pod door removed, allows a robot arm todeliver/remove a wafer to/from the cavity.

The present invention is further directed to a method for calibrating arobot arm by a calibration cassette pod which includes the operatingsteps of first providing a cassette pod body and a cassette pod door,the cassette pod body is constructed of a top panel, a bottom panel, twoside panels and a front panel defining a cavity therein; providing afirst plurality of ribs on an inside surface of the two side panels andthe front panel each has a preset depth sufficient to support an edgeportion of a wafer; mounting an optical detector housing on an openingin the front panel adapted for receiving an optical detector therein,the optical detector may further include a light emission source and aphoto diode receiver for determining the position of the edge portion ofthe wafer; providing a process controller for receiving signals from thelight emission source and the photo diode receiver; manually operatingthe robot arm and loading a wafer into the cavity such that the edgeportion of the wafer is positioned in-between the light emission sourceand the photo diode receiver and in a correct position on top of one ofthe first plurality of ribs; resetting a reading on the processcontroller to zero; and automatically operating the robot arm andloading a wafer into the cavity obtaining a new reading on the processcontroller and determining its deviation from zero.

The method for calibrating a robot arm by a calibration cassette pod mayfurther include the step of providing a second plurality of lightemission units and a second plurality of photo diode receivers. Themethod may further include the step of providing six light emissionunits arranged in a single row and six photo diode receivers arranged ina single row positioned in a mirror image to the six light emissionunits. The method may further include the step of resetting a reading onthe process controller to zero when the edge portion of the wafer blocksthree adjacent light emission units from three corresponding photo diodereceivers. The method may further include the step of emitting a visiblelight beam from the light emission source.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will become apparent from the following detailed descriptionand the appended drawings in which:

FIG. 1 is a perspective view of a cassette pod mounted on a loadport ofa process machine.

FIG. 2 is a perspective view of a cassette pod with a removable backpanel for 300 mm wafers.

FIG. 3 is an exploded, perspective view of the present inventioncalibration cassette pod being accessed by a robot arm.

FIG. 3A is a perspective view of a wafer being positioned in-between alight emission source and a photo diode receiver for determining theposition of the edge of the wafer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention discloses a calibration cassette pod for robotteaching and a method of using the pod.

In a preferred embodiment, the present invention calibration cassettepod for robot teaching can be provided which includes a cassette podbody; a cassette pod door; a first plurality of ribs formed on an insidesurface of the cassette pod body; an optical detector housing mounted onan opening in the cassette pod body; and an optical detector mountedinside the optical detector housing.

The cassette pod body of the present invention calibration cassette podmay be constructed of a top panel, a bottom panel, two side panels and afront panel which define a cavity formed therein. In a preferredembodiment, the top panel, the bottom panel and the two side panels areplanar panels, while the front panel is a curvilinear panel. The firstplurality of ribs, or ridges, are formed on an inside surface of the twoside panels and the front panel. The first plurality of ribs should havea predetermined depth that is sufficient for supporting an edge portionof a wafer. The optical detector housing should be mounted on an openingthat is provided in the front panel of the cassette pod body. Theoptical detector housing receives an optical detector which may includea light emission source and a photo diode receiver in the housing fordetermining the position of an edge of a wafer, i.e. for determiningwhether a wafer is placed too far into the slot opening, or not farenough into the slot opening of the housing.

Referring now to FIG. 3, wherein an exploded, perspective view of thepresent invention calibration cassette pod 30 is shown. The cassette pod30 is shown in a cassette pod body 32 with a cassette pod door (notshown) removed. The cassette pod body 32 shown in FIG. 3 is shown forillustration purposes only and therefore, does not necessarily representthe true shape of a cassette pod which is more likely similar to thatshown in FIG. 2. In the front panel 34 of the cassette pod body 32, isprovided an opening 36 onto which an optical detector housing 38 ismounted thereto. It should be noted that while the optical detectorhousing 38 is shown in a rectangular shape for illustration purposes,any other suitable shape may also be utilized.

Inside the optical detector housing 38 is mounted an optical detector 40which consists of a light emission source 42 and a photo diode receiver44. The light emission source 42 may consists of a plurality of lightemission units, i.e. such as at least three light emission units, orpreferably at least six light emission units 54, shown in FIG. 3A.Similarly, the same number of photo diode receivers 56 are provided andare positioned in mirror image to the six light emitting units 54 in aspaced-apart relationship. The distance between the light emission units54 and the photo diode receivers 56 should be sufficient, i.e. at leasttwo to three times the thickness of a wafer, to allow the placement of awafer 60 therein between during a calibration process.

Also shown in FIG. 3 is a robot arm 70 which is equipped with a waferblade (not shown) mounted at the tip portion of the robot arm forcarrying a wafer 60 thereon. A numerical display panel 62 may also beprovided and mounted on top of the top panel 26 of the cassette pod body32. The digital display panel 62 may show a display of the distance intothe optical detector 40 that the wafer 60 has penetrated. It should benoted that while six light emission units 54 and six photo diodereceivers 56 are provided in the preferred embodiment, any othersuitable numbers such as four, five or up to ten may be utilized whenarranged in a straight line for detecting the presence of a wafer edgetherein between.

The present invention novel method utilizing the apparatus shown inFIGS. 3 and 3A can be carried out by the following operating steps:

-   -   1. Providing a cassette pod body 32 and a cassette pod door (not        shown in FIG. 3), the cassette pod body 32 may be constructed of        a top panel 26, a bottom panel 24, two side panels 20,22 and a        front panel 34 to define a cavity 58 therein.    -   2. Providing a first plurality of ribs 64 on an inside surface        of the two side panels 20,22 and the front panel 34 such that        each of the plurality of ribs has a preset depth sufficient to        support an edge of a wafer 60.    -   3. Mounting an optical detector housing 38 on the opening 36 of        the front panel 34. The optical detector housing 38 is adapted        for receiving an optical detector 40 therein. The optical        detector 40 may include a light emission source 42 and a photo        diode receiver 40 for determining the position of the edge        portion 72 of the wafer 60.    -   4. Providing a process controller 74 which has a digital display        panel 62 mounted thereon for receiving signals from the light        emission source 42 and the photo diode receiver 40.    -   5. Manually operating the robot arm 70 and loading a wafer 60        into the cavity 58 such that the edge portion 72 of the wafer 60        is positioned in-between the light emission source 42 and the        photo diode receiver 40 and in a correct position on top of one        of the plurality of ribs 64.    -   6. Resetting a reading on the digital display panel 62 of the        process controller 74 to zero.    -   7. Automatically operating the robot arm 70 and loading a wafer        60 into the cavity 58 to obtain a new reading on the process        controller 74 and determining its deviation from zero.

The present invention novel apparatus of a calibration cassette pod forrobot teaching and a method for using the pod have therefore been amplydescribed in the above description and in the appended drawings of FIGS.3 and 3A.

While the present invention has been described in an illustrativemanner, it should be understood that the terminology used is intended tobe in a nature of words of description rather than of limitation.

Furthermore, while the present invention has been described in terms ofa preferred embodiment, it is to be appreciated that those skilled inthe art will readily apply these teachings to other possible variationsof the inventions.

The embodiment of the invention in which an exclusive property orprivilege is claimed are defined as follows.

1. A calibration cassette pod for robot teaching comprising: a cassettepod body and a cassette pod door, said cassette pod body is constructedof a top panel, a bottom panel, two side panels and a front paneldefining a cavity therein; a first plurality of ribs formed on an insidesurface of said two side panels and said front panel each having apreset depth sufficient for supporting an edge portion of a wafer; anoptical detector housing mounted on an opening in said front paneladapted for receiving an optical detector therein; and an opticaldetector comprising a light emission source and a photo diode receiverfor determining the position of said edge portion of the wafer.
 2. Acalibration cassette pod for robot teaching according to claim 1,wherein said light emission source comprises a second plurality of lightemission units and a second plurality of photo diode receivers.
 3. Acalibration cassette pod for robot teaching according to claim 1,wherein said second plurality is at least three.
 4. A calibrationcassette pod for robot teaching according to claim 1, wherein saidsecond plurality is preferably at least five.
 5. A calibration cassettepod for robot teaching according to claim 1 further comprising a processcontroller for receiving signals from said optical detector andcomparing to a stored datum.
 6. A calibration cassette pod for robotteaching according to claim 1, wherein said light emission source emitsa visible light beam.
 7. A calibration cassette pod for robot teachingaccording to claim 5 further comprising a robot arm controlled by saidprocess controller.
 8. A calibration cassette pod for robot teachingaccording to claim 2, wherein said optical detector is mounted in saidoptical detector housing with said second plurality of light emissionunits and said second plurality of photo diode receivers protruding intosaid cavity of said cassette pod body.
 9. A calibration cassette pod forrobot teaching according to claim 1, wherein said cassette pod body wheninstalled on a loadport of a process machine with said cassette pod doorremoved, allows a robot arm to deliver/remove a wafer to/from saidcavity.
 10. A method for calibrating a robot arm by a calibrationcassette pod comprising the steps of: providing a cassette pod body anda cassette pod door, said cassette pod body being constructed of a toppanel, a bottom panel, two side panels and a front panel defining acavity therein; providing a first plurality of ribs on an inside surfaceof said two side panels and said front panel each having a preset depthsufficient for supporting an edge portion of a wafer; mounting anoptical detector housing on an opening in said front panel adapted forreceiving an optical detector therein, said optical detector comprisinga light emission source and a photo diode receiver for determining theposition of said edge portion of the wafer; providing a processcontroller for receiving signals from said light emission source andsaid photo diode receiver; manually operating said robot arm and loadinga wafer into said cavity such that said edge portion of the wafer ispositioned in-between said light emission source and said photo diodereceiver and in a correct position on top of one of said first pluralityof ribs; resetting a reading on said process controller to zero; andautomatically operating said robot arm and loading a wafer into saidcavity obtaining a new reading on said process controller anddetermining its deviation from zero.
 11. A method for calibrating arobot arm by a calibration cassette pod according to claim 10 furthercomprising the step of providing a second plurality of light emissionunits and a second plurality of photo diode receivers.
 12. A method forcalibrating a robot arm by a calibration cassette pod according to claim10 further comprising the step of providing six light emission unitsarranged in a single row and six photo diode receivers in a single rowpositioned in a mirror image to said six light emission units.
 13. Amethod for calibrating a robot arm by a calibration cassette podaccording to claim 12 further comprising the step of resetting a readingon said process controller to zero when said edge portion of the waferblocks three adjacent light emission units from three correspondingphoto diode receivers.
 14. A method for calibrating a robot arm by acalibration cassette pod according to claim 10 further comprising thestep of emitting visible light beam from said light emission source.